Structural characterization and confined pyrolysis of resistant aliphatic biopolymer derived from cyanobacteria

Abstract

Two cultured cyanobacteria species were divided into three fractions, investigated using Rock-Eval, elemental analysis, and 13C cross polarization/total sideband suppression (CP/TOSS) nuclear magnetic resonance (NMR) to obtain information on the structure, composition, and oil and gas production potential (OGP) of these species. Confined pyrolysis experiments were performed on isolated acid nonhydrolyzable organic matter (NHOM) fractions. The results showed that the NHOM fractions from Oscillatoria sp. (OSC_NHOM) and Calothrix anomala (CAL_NHOM) were similar to the highly aliphatic algaenan in structure and capable of generating gas and oil. Pyrolysis experiments of the OSC_NHOM and CAL_NHOM fractions demonstrated that they contained a saturated and unbranched carbon chain with up to 33 carbon atoms and had high OGP. The maximum oil yield (59% for OSC_NHOM and 47% for CAL_NHOM) derived from the pyrolysis experiments was higher than that from oil-prone carbon (46% for OSC_NHOM and 39% for CAL_NHOM), suggesting that the 13C CP/TOSS NMR method slightly underestimates the oil production potential of cultured cyanobacterial (and possibly algal) biopolymers. Our investigation confirms the presence of algaenan-like biopolymers in a broader suite of cyanobacteria.